Abstract The rock mass deformation modulus, Erm, is an input parameter for most numerical modeling to verify the deformation behavior of rocks due to rock engineering activities within/on it. Among the most common methodologies used for estimating this parameter, empirical correlations based on rock mass classification schemes (e.g., RQD, RMR, GSI, and Q) stand out the most, principally because of their low cost when compared to the other methods. Herein, the main correlations used in practice are evaluated and comparted for 48 different rock quality scenarios, previously characterized and classified according to rock mass classification systems. The results obtained by each of the empirical correlations demonstrated that normalized correlations, that is, based on the ratio of the rock mass and intact rock modulus, Erm/Ei, underestimate the Erm values when compared to those results obtained from not-normalized correlations in the scenarios of better quality rock masses. For poor quality rock mass scenarios, both non-normalized and normalized correlation presented similar results. The correlations proposed by Hoek and Diederichs (2006) and Galera et al. (2007) estimated more central Erm values when compared to the other correlations, for all quality scenarios, while the Mitri et al. (1994) and Sonmez et al. (2006) methods estimated most high and low values of Erm, respectively.

RESUMO O elevado custo de aquisição e o longo período de tempo para obter a curva de retenção pelo método convencional utilizando a câmara de Richards e o funil de Haines restringem o uso desses, sendo interessante a busca por métodos alternativos que agilizem a rotina. Diante disso, avaliou-se o método do papel-filtro para obter a curva de retenção de água do solo em comparação com o método convencional. Coletaram-se amostras indeformadas de cinco diferentes solos. Utilizando-se o funil de Haines e a câmara de Richards, obtiveram-se as umidades nas tensões 2, 4, 6, 8, 10, 33, 100, 300, 700 e 1.500 kPa. No ensaio com o papel-filtro, obteve-se o potencial matricial da água por meio da equação de calibração do papel-filtro; posteriormente, a umidade foi estabelecida pela diferença gravimétrica. O modelo de van Genuchten foi ajustado aos dados de potencial matricial versus umidade. Comparando-se os métodos convencional e papel-filtro por meio dos valores de umidade estimados segundo o modelo de van Genuchten, concluiu-se que o método do papel-filtro, com R2 = 0,99, pode ser utilizado para obter as curvas de retenção de água dos solos agrícolas, sendo o seu uso como alternativa metodológica ao método convencional.

ABSTRACT High cost and long time required to determine a retention curve by the conventional methods of the Richards Chamber and Haines Funnel limit its use; therefore, alternative methods to facilitate this routine are needed. The filter paper method to determine the soil water retention curve was evaluated and compared to the conventional method. Undisturbed samples were collected from five different soils. Using a Haines Funnel and Richards Chamber, moisture content was obtained for tensions of 2; 4; 6; 8; 10; 33; 100; 300; 700; and 1,500 kPa. In the filter paper test, the soil matric potential was obtained from the filter-paper calibration equation, and the moisture subsequently determined based on the gravimetric difference. The van Genuchten model was fitted to the observed data of soil matric potential versus moisture. Moisture values of the conventional and the filter paper methods, estimated by the van Genuchten model, were compared. The filter paper method, with R2 of 0.99, can be used to determine water retention curves of agricultural soils as an alternative to the conventional method.